up until it calcines into lime and CO2) is required in the form of heat. The total heat energy requirement is approximately 2GJ per tonne of limestone calcined which yields a figure of approximately 3GJ per tonne of CO2 sequestered. The exact amounts will depend on the exact process (how much heat from the CO2 generated is recaptured, etc).

Unless we can generate electricity extremely cheaply it is likely to be too expensive to drive this process. Here’s why: 1 kilowatt-hour is 3.6MJ – so 1GJ is approximately 278 kWhrs. If you have cheap electricity at say $0.05 per kWhr, then to generate 1GJ will cost ~$14. In comparison, natural gas can be much cheaper. There are numerous deposits of

‘stranded gas’ where the cost of extracting the gas out of the ground is less than $1 per GJ, but it would cost so much to transport to a market, that it is not worth doing so. Because this process can be performed anywhere where limestone, energy and the sea are in close proximity, it is possible to use that stranded gas.

Electricity is an extremely high-quality form of energy, which is absolutely necessary to run our modern society

(including this computer). But for this process we require heat, not high-quality energy and the process of turning heat (from say a power station) into electricity and then turning the electricity into heat is inefficient and unnecessary. Better to use heat directly.

Thank you to Steaphany Waelder who sent me an email with some contacts

in Australia who are investigating generating high-grade heat from solar irradiation. This is exactly the sort of information that we are looking for. If we can use solar irradiation that would be ideal, as there would be no CO2 from heat generation – my concern is the cost of the equipment and that is what we will be looking into.

Thank you also to Henry Brown with his post on Opensource maps. The code you have written at the end of your post is, I’ll admit, quite beyond me, but I’m told by someone who knows that this will generate maps of the various elements that we need to pull together – genius!